Formation treating methods

ABSTRACT

Disclosed are methods for treating wells to form a permeable barrier around the well for consolidating unconsolidated mineral particles such as sand in a subterranean petroleum formation penetrated by a well, or for forming an impermeable barrier for fluid entry control, or for plugging the well for abandonment. A fluid containing a polymerizable resin such as furfuryl alcohol, a polar organic diluent such as butyl acetate and an oil soluble acid catalyst to cause polymerization of the resin at formation temperatures is prepared. The acid should have a pK in the range of 0.4 to 6.0. The acid and acid concentration are selected to cause the polymerization reaction to be essentially complete in from 0.75 to 4.0 hours and preferably 1.0-2.0 hours at the formation temperature. Usually the selected acid concentration will be in the range of from 0.2 to 5.0 percent. This fluid is injected into the formation to saturate at least a portion of the formation adjacent to the well. In one embodiment, when it is desired to form a permeable treated zone for sand control, an aqueous fluid comprising water which is from 70 to 100% saturated with inorganic salts including sodium chloride is injected into the same portion of the formation contacted by the resin containing fluid. The injected resin-containing fluid is allowed to remain in the formations for at least four hours to accomplish at least partial polymerization of the resin, forming a permeable or impermeable mass around the wellbore.

REFERENCE TO COPENDING APPLICATIONS

This is a continuation-in-part of copending application Ser. No. 718,513filed Jun. 21, 1991, now abandoned, for "SAND CONSOLIDATION METHODS".This application is also related to Pending application Ser. No. 459,604filed Jan. 2, 1990, now U.S. Pat. No. 5,040,604, for SAND CONSOLIDATIONMETHODS.

FIELD OF THE INVENTION

This invention concerns well treating methods including in one importantembodiment, a method for treating wells completed in subterraneanformations containing unconsolidated particulate matter, e.g.unconsolidated sand, in order to bind the unconsolidated sand grainstogether in the portions of the formation immediately adjacent to theperforations of the well, and thereby form in this embodiment a stableyet still fluid permeable barrier around the wellbore, in order tofacilitate production of fluids from the formation while restraining themovement of sand into the wellbore during the fluid production phase. Inanother embodiment, this method results in the creation of anessentially impermeable barrier around the wellbore to exclude flow offluids including water from the formation into the well. In yet anotherembodiment, the area around the well and in the well are filled with animpermeable mass so the well can be abandoned safely. More particularly,this invention pertains to a method for accomplishing sandconsolidation, water exclusion or well plugging in producing oil wellsutilizing the sand naturally present in the formation and a method whichutilizes a substantially reduced number of procedural steps, whichreduces the time and cost of treating wells, by use of single fluidcontaining the polymerizable resins with the catalyst already mixed withthe resin in order to achieve more uniform mixing and to reduce thenecessity of using multiple fluid injection steps to clean the sand orcoat the sand with catalyst. In particular, preferred embodiments ofthis invention permit treating wells completed in formations whosetemperatures are from 60° F. ( 15.5° C.) to 350° F. (176.7° C.) orgreater with set times below 24 hours.

BACKGROUND OF THE INVENTION

Formation treating for purposes of sand consolidation, water exclusionor well plugging for abandonment are well known terms applying toprocedures routinely practiced in the commercial production ofpetroleum. When wells are completed in petroleum-containing which alsocontain unconsolidated granular mineral material such as sand or gravel,production of fluids from the formation causes the flow of theparticulate matter, e.g. sand, into the wellbore, which often leads toany of several difficult and expensive problems. Sometimes a well will"sand up", meaning the lower portion of the production well becomesfilled with sand, after which further production of fluid from theformation becomes difficult or impossible. In other instances, sandproduction along with the fluid results in passage of granular mineralmaterial into the pump and associated hardware of the producing well,which causes accelerated wear of the mechanical components of theproducing oil well. Sustained production of sand sometimes forms acavity in the formation which collapses and destroys the well. All ofthese problems are known to exist and many methods have been disclosedin the prior art and applied in oil fields in order to reduce oreliminate production of unconsolidated sand from a petroleum formationduring the course of oil production.

Another problem encountered in oil production to which the presentprocess offers an attractive solution is encountered when a well is influid communication with a section that includes one or more oilproducing intervals and one or more water producing intervals.Production from such a zone results in production of some oil and somewater. Since the viscosity of water is less than the viscosity of oil, amuch larger volume of water than oil is frequently produced.

In yet another embodiment, the resin-catalyst mixture can be used tocompletely plug a well which is to be abandoned. This embodimentrequires a slightly greater volume of resin-catalyst mixture to be used,since the best results for this embodiment require that the interior ofthe well casing and/or tubing be filled completely with the resin forall or a substantial amount of its length. The long term durability ofthe material used to plug wells for abandonment is of high currentinterest because of the danger that salt water or petroleum might enterand contaminate fresh water-containing 15 intervals.

The above-described sand control problems and potential solutions to theproblems have been the subject of extensive research by the petroleumindustry in the hope of developing techniques which minimize oreliminate the production of sand particles into the producing well andassociated equipment during the course of producing fluids from theformation. One general approach suggested in the prior art forconsolidating sand to form a fluid permeable zone around the wellinvolves consolidating the porous but unconsolidated sand structurearound the wellbore in order to cement the loose sand grains together,thereby forming a permeable mass which will allow production of fluidsfrom the formation into the well but which will restrain the movement ofsand particles into the wellbore when used for fluid exclusion, into animpermeable mass if the desired result is water exclusion. Anotherapproach involves removing a portion of the formation around the welland packing specially prepared granular material into the formationaround the wellbore which is subsequently caused to be cemented togetherin a manner which maintains fluid permeability.

It is a primary objective of any successful sand consolidation methodthat a barrier be formed around the wellbore which restrains themovement of sand particles into the well while offering little or norestriction to the flow of fluids, particularly oil, from the formationinto the wellbore where it can be pumped to the surface of the earth.Consolidation only needs to extend into the formation to a depth of 6 to12 inches around the periphery of the perforations or other openings inthe outer casing of the production well.

The objective of a water exclusion of fluid entry control process is toform an impermeable barrier around the well to prevent the flow of sandand formation fluids into the well. A process similar to that used tocontrol sand problems can be used for plugging formation for waterexclusion, provided the process is modified to cause creation of animpermeable barrier rather than a permeable barrier.

A very important quality of a satisfactory sand consolidation method,plugging or water exclusion method is durability of the permeable orimpermeable barrier formed around the wellbore. Once a permeable barrieris formed and the well is placed on production, there will be acontinuing flow of fluids through the flow channels within the permeablebarrier, and it is important that the barrier last for a significantperiod of time, e.g. several months and preferably years, withoutexcessive abrasive wear or other deterioration of the consolidationmatrix which would cause the particulate matter to flow once again intothe wellbore.

It is also important that the material injected into the formation forall of our formation treating methods described above should beessentially unreactive during the period it is inside the wellbore, i.e.while it is being pumped down the well and positioned where it isdesired adjacent to the perforations of the production casing. It isthis desire to delay the polymerization reaction that has lead prior artmethods to employ multi-step procedures in which first a catalyst isinjected into the formation, after which the polymerizableresin-containing fluid is injected. While this reduces the propensityfor the fluid to polymerize in the wellbore, it does give rise toseveral problems which constitute inherent weaknesses in many prior artmethods for accomplishing sand consolidation. First, each separateinjection step increases the time and cost associated with the welltreatment by which sand consolidation, water shut off or well pluggingis accomplished. Second, injection of catalyst into the formation inadvance of the polymerizable fluid does not accomplish uniform mixing ofcatalyst with all of the polymerizable fluid which is needed to ensureoptimum polymerization of the resin, which is essential for strength anddurability of the consolidated mass. Use of aqueous fluids to injectcatalyst often gives rise to the need for yet additional steps to cleanthe sand to remove formation petroleum so the catalyst will be absorbedby the sand and later mix with the subsequently injected resincontaining fluid.

PRIOR ART

Many processes and materials have been utilized for treating formationsfor consolidating sand in the formation adjacent to production ofwellbores or to plug wells to control fluid entry into the well or toprepare the well for to abandonment. One of the more successful agentsutilized for this purpose is furfuryl alcohol resin which can bepolymerized to form a solid matrix which binds the sand grains together,while at the same time offering superior resistance to high temperaturesand to caustic substances which may be encountered in steam floodoperations. One of the problems in utilizing furfuryl alcohol resin topolymerize in the formation is in accomplishing uniform catalysis of thepolymerization. Many catalysts that are effective for polymerizingfurfuryl alcohol resins cannot be admixed with the furfuryl alcohol topermit employing a single fluid containing both the resin and thecatalyst to be injected into the formation, because the time ofpolymerization is so short or unpredictable that there is excessivedanger that the resin will polymerize in the injection wellbore.

In U.S. Pat. No. 4,427,069 there is disclosed a procedure forconsolidating sand in a formation adjacent to a wellbore using anoligomer of furfuryl alcohol, in which the catalyst used is a watersoluble acidic salt, preferably zirconyl chloride, which is injected inan aqueous solution into the formation prior to the resin containingfluid injection. The salt absorbs on the sand grains, and sufficientacidic salt remains adsorbed on the sand grain during the subsequentresin fluid injection stage that adequate polymerization occurs.Although this has been effective in many difficult situations where sandconsolidation procedures are utilized, specifically in connection withthermal flooding such as steam injection procedures, the procedurenevertheless requires a multi-fluid injection procedure which requiresmore time and is more expensive than is desired. Usually a preliminarysand cleaning step is required before injecting the aqueous-catalystsolution in order to remove the naturally-occurring oil film from thesand grains to ensure good catalyst adsorption on the sand. Also,although catalyst mixes with the subsequently injected polymer to alimited degree, usually sufficient to cause some polymerization, it isbelieved that improved performance would result if the catalyst resinmixture can be made more homogenous prior to polymerization, in order toachieve a dense strong durable consolidation mass.

In U.S. Pat. No. 4,842,072 for "SAND CONSOLIDATION" we disclosed aparticularly effective method for consolidating sand utilizing a mixtureof a polymerizable resin such as an oligomer of furfuryl alcohol and adiluent such as butyl acetate and an oil soluble, slightly water solubleacid catalyst such as orthonitrobenzoic acid which is injected followedby injection of salt water to reestablish permeability.

In U.S. Pat. No. 4,903,770 for "SAND CONSOLIDATION" we disclosed apreferred process which is more easily removed after a period of use andwhich is quite inexpensive. The process employs a fluid comprising apolymerizable monomer such as furfuryl alcohol and as a diluent, a polarorganic solvent such as methanol and a strong, non-volatile acidcatalyst such as sulfuric acid, mixed with steam to form a multiphase oraerosol treating fluid, and injected into the formation to beconsolidated. An ester such as ethyl or butyl acetate is incorporated inthe fluid when the steam quality is less than 80 percent.

In U.S. Pat. No. 4,669,543 which issued Jun. 2, 1987, there is describeda method for consolidating sand using an acid-curable resin andutilizing as a catalyst, the reaction product of an acid, and an alkylmetal or ammonia molybdate. In that instance, the catalyst isincorporated in an aqueous carrier fluid which comprises the continuousphase of an emulsion in which the polymerizable resin is the dispersedor discontinuous phase. Thus this process requires that the emulsion beresolved or broken after it is located in the portion of the formationwhere the permeable consolidating mass is desired, which is difficult toachieve to the high degree of completion necessary to accomplish thedesired strong durable consolidating matrix necessary for a long lastingsand consolidation process.

U.S. Pat. No. 5,010,953 which issued Apr. 30, 1991 teaches a sandconsolidating process using a polymerizable compound such as furfurylalcohol, a diluent such as a low molecular weight alcohol, an acidcatalyst and an ester and as an additive to reduce shrinkage, acopolymer of starch and a synthetic polymer such as acrylamide oracrylate.

U.S. Pat. No. 5,005,647 which issued Apr. 9, 1991, discloses a processfor shutting off permeable zones in wellbores to reduce excess waterflow using fluids similar to that described in U.S. Pat. No. 5,010,953discussed above.

U.S. Pat. No. 5,005,648 which issued Apr. 5, 1991 describes a method oftreating permeable zones in a formation to reduce water flow into a wellcompleted therein by injecting a fluid-containing polymerizablecompound, an ester, and an acid catalyst such as orthonitrobenzoic acidor toluenesulfonic acid.

U.S. Pat. No. 4,938,287 which issued Jul. 3, 1990 describes a process inwhich a preflush such as ethyl or butyl acetate is injected into thesand to be consolidated to remove oily residue, followed by injectingthe treating fluid containing the polymerizable resin, diluent, esterand acid catalyst to accomplish sand consolidation.

The above processes have been extremely successful in treating wells inmany formations, especially in formations where the temperature exceeds350° F. This is highly advantageous since many formations being steamstimulated and which cannot be treated by other processes, can betreated by this process with a high success ratio. When the temperatureis much below 350° F., however, the set time or time required forpolymerization of the furfuryl alcohol often runs several days to oneweek or more. This often causes poor adhesion of the polymerizedfurfuryl alcohol to the sand grains, resulting in a weak consolidationjob. Thus there is still an unfulfilled need for a well treating methodfor sand consolidation, fluid exclusion or plugging wells prior toabandonment applicable to formations whose temperatures span a broadrange including temperatures up to and exceeding 350° F. which willresult in a set time less than 24 hours, preferably from 1-2 hours.

SUMMARY OF THE INVENTION

We have discovered methods for treating wells for consolidating sand orfor forming a fluid-excluding impermeable barrier in formations over abroad temperature range while still providing a set time less than 24hours, e.g. from 0.75 to 4.0 hours and preferably in the range of1.0-2.0 hours. A fluid comprising a polymerizable resin, preferably aderivative such as an oligomer of furfuryl alcohol, a diluent such asethyl or butyl acetate and an oil soluble internal catalyst which cansafely be mixed with the resin on the surface, is injected into the welland in one embodiment, into the surrounding unconsolidated sand. Thecatalyst action is the key to the success of our process, since thisprocess is applied to formations whose temperature may be less than 350°F. The pK or negative of the log of the ionization constant of the acidcatalyst must be chosen carefully to produce a set time in the range of0.75 to 4 hours and preferably from 1-2 hours at the formationtemperature. If the set time is below one hour, especially if it isbelow 0.75 hours, there is danger that the fluid which contains both thepolymerizable compound and the acid catalyst, will polymerize in thesurface mixing equipment or in the injection string. If the set timeexceeds four hours there is danger that the polymerizable compound willbe washed off the sand grains before polymerization occurs, resulting ina poor bond between the polymerized compound and the sand grains and apoor consolidation job or fluid exclusion job. Ideally the oil-solubleacid chosen should have a pK in a fairly narrow range, from 0.4 to 6.0or greater. The preferred acid for our process varies with thetemperature of the formation being treated. The concentration of theacid in the treating fluid must be selected carefully to ensure the settime is from 0.75 to 4.0 and preferably from 1.0 to 2.0 hours. As anexample, usually a concentration of toluenesulfonic acid in the range offrom 0.2 to 5.0 and preferably from 0.4 to 4.0 will result in a set timein the desired range of from 0.75 to 4.0 and preferably 1 to 2 hourswhen the formation temperature is from 60° F. to 180° F. The preciseconcentration of the preferred acid which produces the desired set timein a particular application in a formation whose temperature is known ordeterminable is defined by the formation temperature. The preferredembodiment for the 60°14 180° F. range involves preparation of a mixtureof from 0.2 to 5.0 percent and preferably from 0.4 to 4.0 percenttoluenesulfonic acid, the preferred catalyst for this reaction at thistemperature, and from 20 to 70%, and ideally around 59% of a polarorganic diluent. Our preferred organic diluent is butyl acetate. To thismixture of butyl acetate and toluenesulfonic acid is added from 30 to 80and preferably about 40% resin, e.g. the furfuryl alcohol oligomer. Thishomogenous organic fluid can then be injected via the injection stringinto the formation without danger of premature polymerization. Theinjected mixture of resin, butyl acetate and toluenesulfonic acid, beingoil soluble, simultaneously removes and displaces undesired oil andother oil soluble material coating the sand grains, and ensures athorough contact between the sand grains and the resin-catalyst mixture.When this well treating process is being applied for sand consolidation,the next step is injection of an aqueous saline solution which is from70% to 100% saturated with inorganic salt, preferably sodium chloride,into the resin saturated zone of the formation. This injection stepaccomplishes an opening of flow channels within the void spaces in theformation into which the resin catalyst mixture had been injectedwithout removing the polymerizable resin, an event which would occurwith <70% salt solution, which is important to ensure that the resultingpolymerized resin bonded sand matrix is sufficiently permeable to permitflow of formation fluids from the formation after the sand consolidationprocess is completed. The salt water also modifies the resin coating onthe sand, removing water therefrom, which increases the strength anddurability of the polymerized resin matrix. The brine post-flush is notused when an impermeable barrier is desired. The well is then shut infor a period of from 0.75 to 4.0 hours and preferably from 1-2 hours.This two-step procedure results in the formation of a permeable,durable, consolidated sand mass around the perforations of the wellborewhich restrains the movement of sand into the wellbore during productionoperations, while permitting relatively free flow of formation fluids,particularly formation petroleum, into the wellbore.

When our well treating process is applied for the purpose of pluggingzones to prevent undesired fluid entry into the well, or to plug anentire well prior to abandonment, essentially the same polymer, diluentand acid catalyst is injected in essentially the same manner, but thesalt water injection step is not used.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

We have discovered, and this constitutes our invention, that it ispossible to accomplish an improved well treating process such as sandconsolidation method, water exclusion or well plugging utilizing thesand naturally occurring in the formation in a process employing asingle treating fluid injection step, plus in some embodiments a brineinjection step. A mixture of polymerizable resin, having dissolved ordispersed therein the catalyst for the polymerization step, and aorganic polar diluent, is injected into the formation to saturate thevoid space in the portion of the formation adjacent to the productionwell. This accomplishes coating the formation granular material, e.g.the formation sand, with the mixture of polymerizable resin andcatalyst. Since the fluid injected into the formation in this step isorganic and contains a diluent, the minor amounts of formation petroleumand other oil-based materials coating and contaminating the surface ofthe sand grains is effectively removed or dissolved. It is a particularfeature of this method that a separate preliminary wash step to removematerials coating the sand grains is not required. We have conductedlaboratory tests, using formation sand containing crude oil, to whichadditional oil was deliberately added, and we still obtained successfulconsolidation by this method without any preliminary wash step.

In another embodiment of our well treating process, the same fluid isinjected to coat the formation granular material and to fill the voidspaces between the grains completely, to form an impermeable mass whichrestricts fluid movement into or out of the well.

The resin which we have found to be especially preferable for use in ourwell treating process is a furfuryl alcohol oligomer. Any resin whichwill polymerize upon exposure to heat and contact with an acid catalystcan be used in this process; however, furfuryl alcohol oligomer (C₄ H₃OCHO)_(n) is the particularly preferred polymerizable resin. This resinhas the advantage of being relatively inexpensive and having thecharacteristic of autopolymerizing on exposure to acid catalyst, forminga thermal-setting resin which cures to an insoluble mass that is highlyresistant to chemical attack as well as to thermal degradation. Theparticularly preferred commercial form in which this resin is availableis "QUACORR 1300" marketed by QO Chemicals. This resin is ordinarilyobtained commercially in a form containing 90 to 95 percent furfurylalcohol oligomer.

The furfuryl alcohol oligomer emulsion utilized in our process is soviscous that it must be diluted with an appropriate solvent in order topermit it to be pumped into the formation, and to accomplish relativelycomplete filling of void spaces in the formation. Any solvent for thefurfuryl alcohol oligomer would accomplish this objective. It ispossible, however, to accomplish this and another important objective byusing as the diluent a hydrolyzable ester. The polymerization of thefurfuryl alcohol oligomer produces water and the water produced bypolymerization eventually limits the polymerization reaction. If waterproduced during polymerization of furfuryl alcohol oligomer can beremoved, it is possible to force the polymerization reaction to proceedfurther toward completion and thereby produce longer polymer chains thanwould result if water were left in the polymer reaction mass. Ahydrolyzable ester will remove water as it is produced, leading to theformation of longer chain polymers which result in a stronger, moredurable polymer matrix which binds the sand grains together.Accordingly, our preferred diluent for the furfuryl alcohol oligomer isa hydrolyzable ester, and our especially preferred species is butylacetate. Other preferred esters are methyl acetate, ethyl acetate andpropyl acetate.

It is essential for this procedure that the acid catalyst utilized beoil soluble so that it may be incorporated in the resin solventsolution. This permits thorough mixing of the catalyst which isessential in order to ensure that the polymerization reaction occursuniformly throughout the entire mass of well treating chemical placed inthe formation. Prior art methods which utilize a catalyst injected in anon-miscible fluid either before or after injection of the fluidcontaining the polymerizable resin, or present in a non-miscible phaseof an emulsion polymer fluid, do not accomplish uniform reactions suchas are possible by use of the present soluble catalyst. The catalyst foruse in our invention must also be one which exhibits temperaturesensitivity such that the catalytic polymerization does not occur duringthe time that the fluid is prepared and mixed on the surface of theearth or pumped into the formation. It is equally important that oncethe fluid is placed in the formation and left in a quiescent state for aperiod of time sufficient to ensure temperature equalization with theformation, that the polymerization reaction occur rapidly in order topermit completion of the procedure in an relatively brief period oftime, so the well can be put on production as soon as possible. Becauseof this dual requirement, the catalyst choice and concentration are bothvery critical to the proper function of our invention.

As stated above, the preferred catalyst for use in our process is onewhich is oil soluble and very slightly water soluble. While we havepreviously disclosed that the preferred organic acid catalyst isorthonitrobenzoic acid for processes being applied to relatively hightemperature (e.g., greater than 350° F.) formations, we have found thatat temperatures less than 350° F. and especially when the formationtemperature is below 300° F., orthonitrobenzoic acid is so weak and soinsoluble that the time required for polymerization to proceed at leastsufficiently far that no displacement of polymer from the sand grainoccurs, is in the range of several days to a week or more. This long settime causes several problems. The polymerizable compound, e.g. thefurfuryl alcohol, may be washed off the sand grains beforepolymerization proceeds far enough to render the polymer immobile, whichgreatly weakens the strength of the polymerized mass. Also, the totalcost of a well treatment is greatly increased by the extended periodwhich the well is shut in, which delays returning the well toproduction.

We have found that the desired set time of from 0.75 to 4.0 andpreferably from 1-2 hours can be realized for any particular formationtemperature in the range of 60° F. to greater than 350° F. andespecially from 100 to 350° F. if the pK of the acid catalyst and theconcentration of the acid catalyst are carefully selected.

The pK of an organic acid is defined as the negative of the log of theionization constant of the acid and is essentially an inverse scalemeasure of the strength of the acid, e.g. strong acids have lower pKvalues. The acid catalyst for this process is preferably an organic acidwhich is oil soluble and which has a pK in the range of 0.4 to >6.0.There is an especially preferred acid for our process for each ofseveral temperature ranges. For example, if the temperature is from 60°F. to 180° F., the acid pK should be from 0.4 to 0.8 and the especiallypreferred catalyst is toluenesulfonic acid, usually p-toluenesulfonicacid, although mixed isomers may also be used. In this range,hydrochloric acid, nitric acid and sulfuric acid are also preferredacids. Mixtures of toluenesulfonic acid with the above may also be used.For convenience, a mixture comprising 95% toluenesulfonic acid with 5%xylenesulfonic acid has been used in the field because the mixture isliquid at field surface conditions and therefore easier to mix with theother fluids in preparing the treating fluid. This is a commercialproduct available under the trade name WITCAT TX ACID® from Witco. Othermixtures may also be used, to ensure that the melting point is belowambient temperature.

When the temperature of the portion of the formation being treated isfrom 180° F. to 250° F., the acid pK should be from 0.8 to 2.1 and theespecially preferred acid is oxalic acid. Other preferred acids for thistemperature range are iodic acid, maleic acid, dichloroacetic acid andtrichloracetic acid.

When the temperature range is from 250° F. to 350° F., the pK should be2.1 to 4.2 and the especially preferred acid is 0-nitrobenzoic acid.Other preferred acids are chloroacetic acid and phosphoric acid.

When the temperature exceeds 350° F., the acid pK should be greater than4.2 and the especially preferred acids are acetic acid, benzoic acid andadipic acid. This information is given in Table I below:

                  TABLE I                                                         ______________________________________                                        Temperature °F.                                                                     pK          Examples                                             ______________________________________                                         60-180      .4 to .8    Toluene Sulfonic                                                              Acid, Hydrochloric                                                            Acid, Sulfuric                                                                Acid, Nitric Acid                                    180-250       .8 to 2.1  Oxalic Acid, Iodic                                                            Acid, Maleic Acid,                                                            Di or Trichlro-                                                               acetic Acid                                          250-350      2.1 to 4.2  Chloroacetic Acid,                                                            Phosphoric Acid,                                                              o-Nitrobenzoic Acid                                  350+         >4.2        Benzoic Acid,                                                                 Acetic Acid, Adipic                                                           Acid                                                 ______________________________________                                    

Once the acid has been selected, the acid concentration should bedetermined. The concentration of a particular acid to yield the desired0.75-4.0 hour set time is solely determined by the formationtemperature. It is essential in applying our process to a formation thatthe temperature of the formation be known or measured. The followingtable gives the relationship between toluenesulfonic acid catalyst andtemperature to produce set time within the preferred 1-2 hour range.

                  TABLE II                                                        ______________________________________                                        FORMATION       % TOLUENE-                                                    TEMPERATURE     SULFONIC                                                      °F.      ACID                                                          ______________________________________                                        Up to 80° F.                                                                           5.0-3.8                                                        80-120° F.                                                                            3.8-3.1                                                       120-140° F.                                                                            3.1-2.4                                                       140-200° F.                                                                            2.4-1.4                                                       200-230° F.                                                                            1.4-0.8                                                       230-260° F.                                                                            0.8-0.5                                                       260-300° F.                                                                            0.5-0.3                                                       ______________________________________                                    

As can be seen from Table II, it is possible to use toluenesulfonic acidover a broader temperature range than the 60° F.-180° F. range for whichthis acid is the preferred catalyst; however, it is preferred that aweaker acid be employed in the 180° F. to 300° F. range for optimumresults and to reduce the sensitivity of the treating fluid to smallerrors in acid concentration.

Surprisingly, we have found that the above correlation holds for anymixture ratio of resin and ester, e.g. butyl acetate, over the volumeratio 90 to 10 to 40 to 60.

Table III below gives the concentrations of oxalic acid which results inreaction times in the desired range.

                  TABLE III                                                       ______________________________________                                        FORMATION     CONCENTRATIONS OF                                               TEMPERATURE   OXALIC ACID                                                     °F.    Wt. %                                                           ______________________________________                                        180-200       5.0-4.0                                                         200-220       4.0-3.0                                                         220-240       3.0-2.0                                                         240-260       2.0-1.0                                                         ______________________________________                                    

In Table IV, the concentration of o-nitrobenzoic acid which producesreaction times in the desired range are given:

                  TABLE IV                                                        ______________________________________                                        FORMATION     CONCENTRATIONS OF                                               TEMPERATURE   O-NITROBENZOIC ACID                                             °F.    WT. %                                                           ______________________________________                                        250-270       2.5-1.8                                                         270-290       1.8-1.4                                                         290-310       1.4-0.8                                                         310-330       0.8-0.5                                                         330-350       0.5-0.3                                                         ______________________________________                                    

In Table V below, the concentrations of benzoic acid to yield reactiontimes the desired range are given.

                  TABLE V                                                         ______________________________________                                        FORMATION     CONCENTRATIONS OF                                               TEMPERATURE   BENZOIC ACID                                                    °F.    WT. %                                                           ______________________________________                                        350-400       4.0-3.0                                                         400-450       3.0-2.0                                                         ______________________________________                                    

One preferred method for forming a particularly effective fluid for usein practicing the well treating process of our invention involves mixingan approximately 50-50 mixture of the resin in its commercial form,which is usually an emulsion, with butyl acetate, after which the acidsuch as toluenesulfonic acid catalyst is dissolved in this mixture ofresin and ester.

The melting points of many of our preferred acids are above surfaceambient temperatures. For example, the melting point of toluenesulfonicacid is 223° F., so it is necessary to incorporate the acid in asuitable diluent, usually a low carbon alcohol such as methanol, tofacilitate mixing it with the resin emulsion. From 2 to 5 percentmethanol is usually adequate for this purpose. This procedure may beused when applying the fluids described above for sand consolidation,when the well treatment is being used to shut off undesired water flow,or when the fluids are injected to completely plug a well, such as whenthe well is being prepared for abandonment.

The quantity of the fluid comprising the resin, diluent and catalystinjected into the formation varies depending on the purpose to be servedby the treatment, e.g. sand consolidation, fluid entry prevention orcomplete well plugging for abandonment. The volume also varies with thethickness and porosity of the formation to which the well treatingprocess is to be applied, as well as the diameter of the well and thedesired thickness of the treated zone in the formation. The thicknessand porosity of the formation and the diameter of the well will alwaysbe known, and it is ordinarily satisfactory if depth of the penetrationis in the range of from 6 to 12 inches from the well bore. As anexample, if it is desired to treat a formation whose thickness is 18feet and porosity is 35% to form a permeable barrier for sand controljust outside the perforations of the wellbore which is 8 inches (0.67ft.) thick, and the well being treated is 10 inches in diameter(radius=5 in.=0.42 ft), then the volume of fluid necessary is calculatedaccording to the example below. ##EQU1##

About the same volume of salt water is used to create the permeabletreated zone when the well treating method is being used for sandcontrol.

About the same volume of resin-containing fluid will be required totreat an otherwise identical well to form a fluid impermeable barrieraround the well for the purpose of reducing or preventing flow of fluidinto the well. No salt water injection is used in this embodiment.

When a well is to be plugged completely as a step in preparation forabandonment, a greater volume of fluid will be required, since it isnecessary in this embodiment to treat a portion of the permeableformation outside the well perforations as above, and also to fill allor a major portion of the inside of the well casing or tubing, or of anopen hole. In this case, the volume of fluid required for the same welldescribed above is the amount shown in the above example plus enough tofill the inside of the well for 18 feet. The amount required is:##EQU2##

After the above described quantity of fluid comprising resin, catalystand diluent are injected into the formation, a second step is neededwhen our process is being used to form a permeable barrier for sandcontrol. The polymerizable resin must be displaced from the injectionstring to avoid the possibility that the resin might polymerize in thewellbore, also the fluid injected into the formation occupiesessentially all of the void space of the formation, e.g. the volumeother than the sand grains themselves in the portion of the formationcontacted by the fluid. If this injected fluid polymerized withoutinjecting any second fluid to displace a portion of the resin materialfrom the void spaces of the formation, the resultant barrier would bestrong and resistant to chemical attack but it would not be sufficientlypermeable to permit flow of fluid through the formation into thewellbore. For this same post-flush fluid must be used to reestablishfluid permeability in the treated zone.

The polymerizable resin used to prepare the sand consolidation matrix isnormally available commercially as a mixture containing about 5 percentwater. Additional water is formed by the condensation polymerizationreaction. The strength of the sand consolidating polymer matrix will beincreased if at least a portion of this water is removed before theresin polymerizes. We have found that the desired objective ofdisplacing resin from the injection string for developing permeabilitywithin the sand consolidated mass and dewatering the polymer-containingfluid is best accomplished by injecting brine or water containing aninorganic salt, preferably sodium chloride, into the string to displacethe residual amount of resin fluid from the injection string, and alsoto pass through the portion of the formation occupied by the resinfluid. Injection of the brine develops permeability within the treatedportion of the formation which ensures that after the resin haspolymerized, the resultant barrier will be permeable to the flow offluids. The salinity of water utilized in this procedure is quiteimportant. The surface of the resin coated sand grains should bedewatered in order to aid in the polymerization reaction and also inorder to produce a denser stronger matrix cementing the sand grainstogether. Fresh water or water containing up to 70 percent salt does notaccomplish the drying action necessary to produce the desired strengthin the permeable barrier. The desired results will only be achieved ifthe second fluid injected into the formation is at least 70% saturatedwith respect to the inorganic salt. It is preferably at least 80%saturated with salt. Our particular preferred embodiment usesessentially saturated brine, specifically water saturated with sodiumchloride at the conditions of injection. By using at least 70% saturatedbrine, the desired development of permeability is achieved withoutdisplacing any of the resin from the sand grains and dehydration of theresin necessary for the polymerization reaction to occur in the time andto the extent desired for optimum polymerization is also realized. Inpractice, the brine usually is not totally effective at displacing setpolymer from the inside of the injection string. It is usually desirableto drill out any residual polymer before placing the well back onproduction.

As a practical matter, the brine utilized will probably be watercontaining mainly sodium chloride because of the cost and availabilityof sodium chloride in the field. This is a particularly preferred brinefor our purpose. We have discovered that potassium chloride does notwork well in this application, and so the fluid injected into theformation after the polymerization fluid has been injected should notcontain appreciable quantities of potassium chloride. The quantity ofbrine injected into the formation for sand consolidation should besufficient to displace all of the residual resin fluid from theinjection string, and also sufficient to pass through the resinsaturated portion of the formation. It is generally sufficient if aboutthe same volume of brine as the polymerization fluid is utilized, andthe rate at which it is injected is not particularly critical for ourpurposes. As a practical matter, the brine usually is not totallyeffective at displacing set polymer from the inside of the injectionstring. It is usually desirable to drill out any residual polymer beforeplacing the well back on production.

When our well treatment process is used to form an impermeable barrierfor fluid entry prevention, e.g. to reduce flow of water into the well,little or no brine is used. Although enough brine could be injected toflush all of the resin from the well interior, this is difficult tocontrol. We have found it preferable to leave the resin-containing fluidin the well until it has set, and then drill out the well to remove theset resin to a point at least as deep as the bottom perforation fromwhich production is taken. In some cases, the well is drilled out forfrom 10 to 50 feet below the lowest production level to create a void(called a rat hole in the field) into which sand and other solids canfall and accumulate and thereby delay the time when it will becomenecessary to suspend oil production and bail out the well.

After the above steps of injecting the polymerization fluid and whenapplying the process for sand consolidation, the sodium chloridesolution or brine are completed, the well should be shut in and left tostand for a period of from 1 to 4 and preferably at least 1 to 2 hours.

In application of either the sand consolidation, well plugging or watershut off embodiments of our invention, leaving the well shut in for morethan 2 hours will have no adverse effect on the process, and indeed thestrength of the polymerized resin may increase in this additionalperiod. The set time as described herein only defines the minimum timein which polymerization of the resin will proceed to a sufficient levelto prevent washing the polymer from the sand grains.

EXPERIMENTAL SECTION

A series of experiments were performed under controlled laboratoryconditions to determine the concentration of various preferred acidswhich produced a set time in the preferred 1.0-2.0 hour range overappropriate temperature ranges. The following Tables give the observedresults.

                  TABLE VI                                                        ______________________________________                                                      CONCENTRATION OF                                                DOWNHOLE      % TOLUENESULFONIC                                               TEMPERATURE   ACID, WT. %                                                     ______________________________________                                         60° F.                                                                              4.0                                                             100° F.                                                                              3.6                                                             140° F.                                                                              2.7                                                             180° F.                                                                              1.8                                                             220° F.                                                                              1.0                                                             240° F.                                                                              0.6                                                             280° F.                                                                              0.4                                                             ______________________________________                                    

                  TABLE VII                                                       ______________________________________                                                       CONCENTRATION OF                                               TEMPERATURE    OXALIC ACID,                                                   °F.     WT. %                                                          ______________________________________                                        180            5.0                                                            200            4.0                                                            220            3.0                                                            240            2.0                                                            260            1.0                                                            ______________________________________                                    

                  TABLE VIII                                                      ______________________________________                                                      CONCENTRATION OF                                                TEMPERATURE   O-NITROBENZOIC ACID,                                            °F.    WT. %                                                           ______________________________________                                        260           2.0                                                             280           1.6                                                             300           1.1                                                             320           0.7                                                             340           0.4                                                             ______________________________________                                    

                  TABLE IX                                                        ______________________________________                                                      CONCENTRATIONS OF                                               TEMPERATURE   BENZOIC ACID                                                    °F.    WT. %                                                           ______________________________________                                        350           4.0                                                             400           3.0                                                             450           2.0                                                             ______________________________________                                    

FIELD EXAMPLE I--SAND CONSOLIDATION

For the purpose of complete disclosure, including what is now believedto be as the best mode for applying the process of our invention, thefollowing pilot field example is supplied.

A producing well is completed in a subterranean petroleum containingformation, the formation being from 8560 to 8588 feet. Considerable sandproduction has been experienced in other wells completed in thisformation in the past, and so it is contemplated that some treatmentmust be applied in order to permit oil production from this formationwithout experiencing the various problems of unconsolidated sandproduction. This particular well has not yet been used for oilproduction, and so little sand has been produced from the formation. Itis known that the sand is coated with formation crude, but is otherwiseof a reasonable particle size to accommodate sand consolidation processusing the natural sand present in the formation. It is decided thereforeto inject the treating fluid of our invention into the formationimmediately adjacent to the perforation of the producing well in orderto bind the naturally occurring sand grains together and form a stablemass which forms a permeable barrier to restrain the flow of formationsand into the well while still permitting the free flow of formationfluids including petroleum through the barrier. It is determined that itis sufficient to treat approximately 12 inches (1 foot) into theformation. Based on experience in this field, it is expected that theporosity of the formation to be treated is approximately 40%. Theoutside casing diameter of the well being treated is ten inches(radius=5.0 in. or <0.417 ft.). The volume of fluid necessary to treatthis portion of formation is determined as follows:

    V=(π(1.0+0.417).sup.2 -π(0.417).sup.2)×(0.40) (28) =64.5 Cu. Ft.=482.76 Gallons

In order to accomplish adequate saturation of the portion of theunconsolidated sand formation adjacent to the production well, a totalof 490 gallons of resin treating fluid is required. The resin employedin this procedure is "QUACORR 1300" obtained from QO Chemicals, which isan oligomer of furfuryl alcohol. The 490 gallons of sand consolidationtreating fluid is formulated by mixing 245 gallons of theabove-described resin with 245 gallons of butylacetate. Since theformation temperature is known to be 200° F., the desired concentrationof toluenesulfonic acid is 1.0%. This requires 40 pounds oftoluenesulfonic acid. In order to facilitate use of toluenesulfonic acidin this application, since the surface ambient temperature is 85° F., amixture comprising 40 pounds toluenesulfonic acid and 4.9 gallons ofmethanol is prepared and then added to the resin-ester mixture. Thisfluid is injected into the formation at a rate of about 900 gallons perhour. After all of the treating fluid has been injected into theformation, 500 gallons of saturated sodium chloride brine is formulatedand injected into the well at the same rate to displace the treatingfluid out of the injection string and to force brine through the portionof the formation into which the treating fluid has been injected,displacing a portion of the treating fluid from the void spaces in theformation thereby forming flow channels in the resin zone. This ensuresthat the residual permeable barrier will exhibit sufficient permeabilityto permit production of fluids from the well. The well is shut in and isleft for a period of 2 hours, which is adequate for this particularformation temperature. At the conclusion of this shut-in soak period,the well is drilled out to remove residual resin from inside the well,and to a point 30 feet below the bottom of the perforations to oreate arat hole where produced sand can settle. The well is then placed onproduction and essentially sand-free oil production is obtained.

FIELD EXAMPLE II--FLUID ENTRY CONTROL

A producing well is completed in a subterranean petroleum containingformation, the petroleum formation being from 8540 to 8588 feet. Thiszone is treated as described above to control production ofunconsolidated sand. Production of oil occurs without sand but excessivesalt water is being produced from a twenty three foot thick zone locatedthirty feet above the oil production zone. It is decided therefore toinject treatment fluid into the water producing interval of theformation in order to form an impermeable barrier to restrain the flowof water into the well. It is determined that it is sufficient to treatapproximately 12 inches (1 foot) into the formation. Based on experiencein this field, it is expected that the porosity of the water producinginterval formation to be treated is also approximately 40%. The outsidecasing diameter of the well being treated is ten inches (radius=5 inchesor 0.417 ft.). The volume of fluid necessary to treat this portion offormation is determined as follows: ##EQU3##

In order to accomplish adequate saturation of the portion of theunconsolidated sand formation adjacent to the production well, a totalof 397 gallons of resin treating fluid is required. The resin employedin this procedure is the same "QUACORR 1300" described above obtainedfrom QO Chemicals, which is an oligomer of furfuryl alcohol. The 397gallons of treating fluid is formulated by mixing 278 gallons of theabove-described resin with 119 gallons of butylacetate. Since theformation temperature is known to be 200° F., the desired concentrationof toluenesulfonic acid is 1.0%. This requires 33 pounds oftoluenesulfonic acid. In order to facilitate use of toluenesulfonic acidin this application, since the surface ambient temperature is 85° F., amixture comprising 33 pounds toluenesulfonic acid and 4 gallons ofmethanol is prepared and then added to the resin-ester mixture. Aretrievable plug is set in the well at a point just below the formationbeing treated. This fluid is injected into the formation at a rate ofabout 900 gallons per hour. After all of the treating fluid has beeninjected into the formation, the well is shut in and is left for aperiod of 2 hours, which is adequate for this particular formationtemperature. The interior of the well is drilled out to remove thehardened resin, and the retrievable plug is removed. At the conclusionof this treatment, the well is placed on production and essentially nowater production is obtained from the treated zone.

FIELD EXAMPLE III--WELL PLUGGING

If the above well is to be abandoned, a treatment similar to Example IIis employed, except the volume of treating fluid is increased so thewell interior is filled from the bottom to the point above the top ofthe upper most perforations, and allowed to solidify. The residual resinin the well is not drilled out in this embodiment.

The additional volume required to fill the bottom 200 ft. of this wellis ##EQU4## This is in addition to the 397 gallons required to seal theformation outside the perforations.

Although our invention has been described in terms of a series ofspecific preferred embodiments and illustrative examples whichapplicants believe to include the best mode for applying their inventionknown to them at the time of this application, it will be recognized tothose skilled in the art that various modifications may be made to thecomposition and methods described herein without departing from the truespirit and scope of our invention which is defined more precisely in theclaims appended hereinafter below.

We claim:
 1. A method for treating a well penetrating a subsurfaceformation and in fluid communication with at least a portion of the asubsurface formation, the temperature of the formation being from 60° F.to 180° F., comprising:(a) selecting an acid catalyst having a pK whichwill cause polymerization of a polymerizable resin at the formationtemperature in from 1 to 24 hours; (b) providing a fluid comprising thepolymerizable resin, a polar organic diluent for the resin, and apredetermined concentration of the oil soluble acid catalyst capable ofcausing polymerization of the resin at formation temperatures, said acidbeing selected from the group consisting of toluene sulfonic acid,hydrochloric acid, sulfuric acid, nitric acid and mixtures thereof; (c)injecting said fluid into the formation to enter and saturate at least aportion of the formation adjacent to the well; and (d) allowing theinjected fluids to remain in the formations for at least four hours toaccomplish at least partial polymerization of the resin, forming aconsolidated resin-sand mass around the wellbore.
 2. A method recited inclaim 1 wherein the resin is oligomer of furfuryl alcohol.
 3. A methodas recited in claim 2 wherein the concentration of the furfuryl alcohololigomer is from 40% to 80% by volume based on the total volume of thefluid.
 4. A method as recited in claim 2 wherein the concentration offurfuryl alcohol oligomer is from 50% to 60% by volume based on thetotal volume of the fluid.
 5. A method as recited in claim 1 wherein thepolar organic diluent is a hydrolyzable ester.
 6. A method as recited inclaim 5 wherein the polar organic diluent is butyl acetate.
 7. A methodas recited in claim 6 wherein the concentration of butyl acetate in thetreating fluid is from 20% to 60% by volume.
 8. A method as recited inclaim 6 wherein the concentration of butyl acetate in the treating fluidis from 20 to 50 percent by volume.
 9. A method as recited in claim 1wherein the concentration of the acid catalyst is selected to causepolymerization of the polymerizable resin at the formation temperaturein from 1 to 4 hours.
 10. A method as recited in claim 9 wherein theconcentration of acid catalyst is from 0.2% to 5.0% by volume.
 11. Amethod as recited in claim 9 wherein the concentration of acid catalystis from 0.40% to 4.0% by volume.
 12. A method as recited in claim 1comprising the additional steps of injecting after the resin-containingfluid has been injected, a second fluid comprising water and inorganicsalts, into the same portion of the formation as the resin containingfluid, to establish permeability in the treated portion of theformation.
 13. A method as recited in claim 12 wherein the aqueous fluidis a sodium chloride brine.
 14. A method as recited in claim 13 whereinthe sodium chloride brine is at least 70% saturated.
 15. A method asrecited in claim 13 wherein the aqueous fluid is saturated sodiumchloride brine.
 16. A method as recited in claim 12 wherein the volumeof aqueous fluid injected into the formation after injecting theconsolidating treating fluid is about equal to the volume of treatingfluid used.
 17. A method as recited in claim 1 wherein theresin-containing fluid is prepared by dissolving catalyst in the polarorganic diluent and then mixing with the resin.
 18. A method as recitedin claim 1 wherein the volume of consolidating treating fluid injectedinto the formation is sufficient to saturate the pore space of theformation adjacent to the producing well for a distance up to 12 inchesfrom the well.
 19. A method as recited in claim 1 wherein the acid istoluene sulfonic acid.
 20. A method as recited in claim 1 comprising theadditional step of pre-dissolving the acid catalyst in a diluentcomprising a low molecular weight alcohol prior to mixing it with thepolymerizable resin and diluent.
 21. A method as recited in claim 20wherein the low molecular weight alcohol is methanol.
 22. A method asrecited in claim 20 wherein the concentration of the low molecularweight alcohol in the mixture of alcohol and acid catalyst is from 1 to5 percent by weight.
 23. A method as recited in claim 1 comprising thestep of injecting sufficient resin-containing fluid to saturate theformation for a distance up to one (1) foot from the well plussufficient additional fluid to fill the well interior for apredetermined distance to prepare the well for abandonment.
 24. A methodfor treating a well penetrating a subsurface formation and in fluidcommunication with at least a portion of the a subsurface formation, thetemperature of the formation being from 180° F. to 250° F.,comprising:(a) selecting an oil soluble acid catalyst which will causepolymerization of an acid catalyzed polymerizable resin at the formationtemperature in from 1 to 24 hours, said acid catalyst being selectedfrom the group consisting of oxalic acid, iodic acid, maleic acid,dichloroacetic acid, trichloroacetic acid, and mixtures thereof; (b)providing a fluid comprising the polymerizable resin, a polar organicdiluent for the resin, and a predetermined concentration of the oilsoluble acid catalyst capable of causing polymerization of the resin atformation temperatures; (c) injecting said fluid into the formation toenter and saturate at least a portion of the formation adjacent to thewell; and (d) allowing the injected fluids to remain in the formationsfor at least four hours to accomplish at least partial polymerization ofthe resin, forming a consolidated resin-sand mass around the wellbore.25. A method as recited in claim 24 wherein the acid is oxalic acid. 26.A method as recited in claim 24 comprising the additional step ofpre-dissolving the acid catalyst in a diluent comprising a low molecularweight alcohol prior to mixing it with the polymerizable resin anddiluent.
 27. A method as recited in claim 26 wherein the concentrationof the low molecular weight alcohol in the mixture of alcohol and acidcatalyst is from 1 to 5 percent by weight.
 28. A method as recited inclaim 24 wherein the low molecular weight alcohol is methanol.
 29. Amethod as recited in claim 24 comprising the step of injectingsufficient resin-containing fluid to saturate the formation for adistance up to one (1) foot from the well plus sufficient additionalfluid to fill the well interior for a predetermined distance to preparethe well for abandonment.
 30. A method for treating a well penetrating asubsurface formation and in fluid communication with at least a portionof the a subsurface formation, the temperature of the formation beingfrom 240° F. to 350° F., comprising:(a) selecting an acid catalysthaving a pK which will cause polymerization of polymerizable resin atthe formation temperature in from 1 to 24 hours, said acid beingselected from the group consisting of chloroacetic acid, phosphoricacid, o-nitrobenzoic acid, and mixtures thereof; (b) providing a fluidcomprising the polymerizable resin, a polar organic diluent for theresin, and a predetermined concentration of the oil soluble acidcatalyst capable of causing polymerization of the resin at formationtemperatures; (c) injecting said fluid into the formation to enter andsaturate at least a portion of the formation adjacent to the well; and(d) allowing the injected fluids to remain in the formations for atleast four hours to accomplish at least partial polymerization of theresin, forming a consolidated resin-sand mass around the wellbore.
 31. Amethod as recited in claim 30 wherein the acid is chloroacetic acid. 32.A method as recited in claim 30 wherein the acid is phosphoric acid. 33.A method as recited in claim 30 comprising the additional step ofpre-dissolving the acid catalyst in a diluent comprising a low molecularweight alcohol prior to mixing it with the polymerizable resin anddiluent.
 34. A method as recited in claim 33 wherein the low molecularweight alcohol is methanol.
 35. A method as recited in claim 30 whereinthe concentration of the low molecular weight alcohol in the mixture ofalcohol and acid catalyst is from 1 to 5 percent by weight.
 36. A methodas recited in claim 30 comprising the step of injecting sufficientresin-containing fluid to saturate the formation for a distance up toone (1) foot from the well plus sufficient additional fluid to fill thewell interior for a predetermined distance to prepare the well forabandonment.
 37. A method for treating a well penetrating a subsurfaceformation and in fluid communication with at least a portion of the asubsurface formation, the temperature of the formation being from 350°F., comprising:(a) selecting an oil soluble acid catalyst having a pKwhich will cause polymerization of an acid catalyzed polymerizable resinat the formation temperature in from 1 to 24 hours, said acid beingselected from the group consisting of benzoic acid, acetic acid, adipicacid and mixtures thereof; (b) providing a fluid comprising thepolymerizable resin, a polar organic diluent for the resin, and apredetermined concentration of the oil soluble acid catalyst capable ofcausing polymerization of the resin at formation temperatures; (c)injecting said fluid into the formation to enter and saturate at least aportion of the formation adjacent to the well; and (d) allowing theinjected fluids to remain in the formations for at least four hours toaccomplish at least partial polymerization of the resin, forming aconsolidated resin-sand mass around the wellbore.
 38. A method asrecited in claim 37 wherein the acid catalyst is acetic acid.
 39. Amethod as recited in claim 37 wherein the acid catalyst is adipic acid.40. A method as recited in claim 37 comprising the additional step ofpre-dissolving the acid catalyst in a diluent comprising a low molecularweight alcohol prior to mixing it with the polymerizable resin anddiluent.
 41. A method as recited in claim 40 wherein the low molecularweight alcohol is methanol.
 42. A method as recited in claim 40 whereinthe concentration of the low molecular weight alcohol in the mixture ofalcohol and acid catalyst is from 1 to 5 percent by weight.
 43. A methodas recited in claim 37 comprising the step of injecting sufficientresin-containing fluid to saturate the formation for a distance up toone (1) foot from the well plus sufficient additional fluid to fill thewell interior for a predetermined distance to prepare the well forabandonment.